When do Prokofiev’s works become public domain?

Question by Altus04: When do Prokofiev’s works become public domain in the US?
IMSLP says only works published before 1923 are safe for download, but wouldn’t all of his material be public domain since Prokofiev passed in 1953? How exactly does the copyright law work? His fifth symphony is from 1944, so I assume I shouldn’t download this in the US. If I am correct, where might I be able to purchase a flute part?
Answers and Views:

Answer by Greg
Right now in the U.S., copyright expires 75 years after the author’s/composer’s death, or if the piece was published before 1923.

To purchase a single part, check J.W. Pepper.

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